1. Field of the Invention
The present invention relates to electronic inventory systems adapted for use with electronic shelf labels, and more particularly relates to systems and methods for enabling communication among such shelf labels and a host system, including networks and systems which are adapted for wireless communication.
2. Description of Related Art
Referring to FIG. 1, retail stores typically display pricing information on paper labels located on shelf edges (shelf labels); FIG. 1 shows an example of a typical printed shelf label. Shelf labels are fitted into C-shaped channels at the edge of product display shelves. Typically, an in-store computer-based printing system downloads “Price Files” from a central location, such as a Retail Chain Headquarters. The information in Price Files is printed on shelf labels and these new shelf labels are manually inserted into the shelf C-channels, usually on a weekly basis. A typical large retail store must update thousands of shelf labels each week.
Referring now to FIG. 2, FIG. 3 and FIG. 4, some Electronic Shelf Labels (ESL) 10 have been produced in an effort to automate the shelf labeling process. As shown in FIG. 4, ESLs 10 display basic price information on a segmented liquid crystal display (LCD).
Referring to FIG. 2, ESLs 10 may receive display information by infrared (IR) or radio frequency (RF) communication 12. Current ESLs 10 often use unidirectional communications techniques to transmit data from the in-store computer-based pricing system to the deployed ESLs 10. Some ESLs 10 are capable of bidirectional communication, allowing the deployed ESLs 10 to send information or requests to the in-store computer system 14. Communication between an in-store computer system 14 and the deployed ESLs 10 is facilitated by one or more access points 16. Access points 16 are often located in the ceilings of the store.
However, the power requirements and limited range for typical prior an electronic shelf labels have led to serious shortcomings. In part, these shortcomings have resulted in prior art display tags extending beyond the shelf C-channels. In addition, such shortcomings have made it necessary to situate costly readers proximate to the tags, leading to costly networks which significantly limit the usability of RFID devices. In part, these shortcomings are associated with the power consumption of the transceiver contained within many such devices. In a typical prior art system, the power amplifier drives the antenna of the RFID device, and antenna power represents a substantial portion of the overall power consumed by the device. In such devices, the input waveform typically has little effect on the output waveform when the input amplitude is less than the turn-on voltage of the active device in the transmitter. In such arrangements, the waveform energy between the negative peak of the input waveform and the turn-on voltage of the active device is not only wasted, but can lead to undesirable parasitic losses.
Thus there has been a need for an RFID system which provides cost-effective, low power communication among electronic shelf labels and their associated host system without requiring excessive size.